Specially formulated slow-release fluid additives that provide for the slow release of additives into a fluid such as oil to meet certain performance requirements of the fluid are generally known. In some, the additives are incorporated into thermoplastic polymers which slowly dissolve into the fluid. In others, the additives are incorporated into polymers which are oil-permeable at elevated temperatures. In still others, the additives are incorporated into particles which are fluid-insoluble but fluid-wettable. In still others, fluid soluble solid polymers are provided, with or without additional additives being incorporated into the polymers.
Although these slow-release fluid additives are capable of introducing additives in the fluid being conditioned, it has been discovered that fluid additive gels can be used more effectively to provide for the slow release of additives into a fluid such as lubricant additives into an oil. In particular, it has been found that fluid-soluble additive gels slowly dissolve to their component fluid additive parts when contacted by the fluid. Examples of such fluid additive gels are disclosed in U.S. patent applications Ser. No. 10/196,441, filed Jul. 16, 2002, Ser. No. 10/603,644, filed Jun. 25, 2003, Ser. No. 10/603,894, filed Jun. 25, 2003 and Ser. No. 10/603,517, filed Jun. 25, 2003, which are incorporated herein by reference.
There is a need for fluid additive delivery systems that allow for the desired contact of the fluid with these fluid additive gels to cause one or more components of the additives in the gels to be slowly released into the fluid.